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19 Oct 2005  -  United States

Reaction injection molding provides alternative to (thermoplastic) injection molding

RIM technology drives global growth of high quality, low cost molded products.
When “injection molding” is mentioned, it is often in reference to thermoplastic injection molding, popular for the manufacture of low cost, molded plastic parts or products. However, despite usurping the category name, injection molding is not the only alternative. Instead, many manufacturers are turning to reaction injection molding (RIM) to produce a superior molded product, and to increase profits by significantly lowering production costs.

Traditional thermoplastic injection molding first evolved from a manual process in the 1940s when machines were little more than presses into which molten plastic was squeezed and then cooled until the part solidified.

Today, injection molding is still widely used, despite the fact that more flexible injection molding processes exist.

With reaction injection molding, chemical components -- typically polyurethanes -- are precisely measured and mixed together by sophisticated metering equipment as they are injected into the mold. The components combine through chemical reaction, and, depending upon the chemical formula, the product can take on a range of characteristics: foam or solid, highly rigid or very flexible.

The RIM molding process provides numerous advantages over injection molding, including:

The “flowability” of the polyurethane components allows for even distribution of the material within the mold. This enables the production of very large parts, not possible with injection molding. RIM molding techniques also allow for the encapsulation of inserts, such as metal frames, which has a range of applications from sports equipment to PC boards.

Another drawback of the traditional molding process has been the inability to produce different wall widths within the same molded part, but RIM allows for the production of significantly varying wall widths.

Additionally, RIM equipment is generally more automated, uses considerably less energy, and requires significantly less equipment and floor space than injection molding.

As for the final product, it is designed to be low weight, scratch resistant, high strength, heat resistant, and resists both organic and inorganic acids. The R-value of polyurethanes make it ideal for insulation in many products, including appliances, ice chests, and coffee cups.

Parts created through the RIM technology include car bumpers, dashboards, snowboards, footwear, sporting goods, medical equipment, furniture, decorative moldings, and mannequins. It’s no wonder that reaction injection molding is billed as “limited only by the imagination.”

“We see tremendous opportunities in RIM markets for new applications,” says Dennis Commette, vice president and general manager of Gusmer | Decker. “The performances of polyurethane materials make it an attractive solution for demanding applications or where higher quality product is required.”

Gusmer | Decker, a leader in the RIM equipment market, manufactures the metering machines and mixing heads central to the process. The company supports all polyurethane production requirements, from single metering machines and mixing heads to equipment for processing multi-component polyurethane and hybrid urethane chemicals.

The continual growth of RIM keeps Gusmer | Decker busy installing factory automation production lines throughout the world.

“We have seen a significant growth in polyurethane product outputs around the world, which in the past made up only a small portion of the reaction injection molding market,” says Commette.

The Gusmer | Decker RIM group is a subsidiary of Graco, Inc., a world leader in fluid handling systems and components.

Source : Gusmer | Decker